With the rapid development of science and technology, video technologies are widely used in various fields for many purposes. For example, video technologies can be used for monitoring a specific visual scene and retrieving a target person from an image of the visual scene. When an original image that is collected by a camera is processed, it is often necessary to identify a target object or a target person from the original image to determine a target image. Conventional systems may determine a target image from the original image by scanning pixels in the original image one-by-one to determine borderlines of the target image in relation to the original image. When the original image has a high resolution, the process of determining borderlines and acquiring the target image from the original image can take a significant amount of time. As a result, overall processing efficiency can be low.